Development of composite materials light in weight and excellent in wear resistance, oxidation resistance, etc. has been desired from the viewpoints of saving of energy, preservation of the environment, etc. For example, carbon fiber-in-composites (hereinafter sometimes referred to as “C/C composites”) have a very high coefficient of friction at high temperatures, and are light in weight and undergo no heat distortion, are widely used as friction materials used in braking devices fitted in large-sized transport machines such as large-sized automobiles and aircraft.
The large-sized transport machines must be sometimes subjected to repeated braking under excess loading for emergent stopping, breaking over a long period of time, and frequent braking, etc. and, hence, in the case of braking devices using C/C composites as friction materials, the friction materials are exposed to high temperatures for a long time in the air. It has been reported that since the friction materials basically comprise, as a main component, carbon fibers which readily burn at high temperatures, the carbon fibers react with oxygen under the above conditions which causes serious wear and also smoking, which sometimes bring about serious accidents. However, materials substitutable for C/C composites have not yet been discovered from the points of frictional force under high temperatures and flexibility required for fitting them in disc brakes.
Under the circumstances, as braking friction materials which can be considerably reduced in wear in the presence of oxygen, even if used as braking friction materials of large-sized transport machines which unavoidably generate high temperature with holding the excellent characteristics of C/C composites (composite carbon fibers), such as excellent impact resistance and light weight and, thus, which are not needed to be frequently exchanged, the inventors have proposed in JP-A-2000-81062 a braking member characterized by comprising a fiber composite material having a yarn aggregate of yarns containing at least bundles of carbon fibers and carbon components other than carbon fibers wherein the yarns are three-dimensionally combined while being oriented in the layer direction and are integrated so as not to separate from each other, and a matrix comprising an Si—SiC material filled between the adjacent yarns in the yarn aggregate.
The braking friction material disclosed in the above patent publication is composed of a composite material comprising ceramics-metal-carbon in which a layer of an Si—SiC material is provided on a base material of a C/C composite. Since the Si—SiC material is formed as a matrix layer of the fiber composite material, the strength of the fibers in the lamination direction increases, and peeling can be inhibited. As a result, durability can be imparted to the braking member. However, for the formation of the matrix comprising the Si—SiC material, it is necessary that the base material which is a C/C composite is impregnated with metallic silicon and then the impregnated product, is fired under desired conditions.
In order to impregnate the C/C composite, which is a laminate having the above construction with metallic silicon, special facilities for carrying out delicate control of temperature, pressure and atmosphere and considerable skill and time are required, and thus further improvement is desired. Moreover, the base material per se has a special structure as mentioned above and hence is not necessarily cheap, and therefore there has been desired development of composite materials having designing performance depending on the use, the manner of use, etc. for completing the articles so as to be able to select such products as being able to exhibit desired performances from the wider groups of products depending on the use, the manner of use, etc., utilizing such base materials as being available more cheaply.